Polar bears in the modern world: Survival prospects

29 November 2011

Polar bears are the only land mammal species that primarily hunt and reproduce on drifting Arctic sea ice. Polar bears spend virtually their entire lives on sea ice. Presently, polar bear survival prospects are uncertain due to the rapidly melting Arctic Ocean ice cover. Some experts on polar bears claim that the animals will become extinct with the disappearance of the sea ice. This assertion sounds like a verdict.

How fatal is melting sea ice for polar bears? What factors are actually threatening polar bears in the modern world? The answers to these questions will determine the course of action in an effort to save the polar bear population.

The Wrangel Island State Nature Reserve has been studying the polar bear’s habitats and behaviour for over 20 years. The reserve’s studies suggest that the future of the polar bear may be dramatic but not so equivocal.

Wrangel Island is known as a major breeding ground for polar bears and as their “maternity ward”. However, the significance of this Arctic Russian island in the life of polar bears is much greater. The island is located in the central section of a vast shelf area that allows for high biological productivity. Polar bears are attracted to the region because it abounds in seals and walruses, their main food. When ice floes disintegrate, polar bears are forced to relocate to the mainland. Wrangel Island becomes a veritable ‘Noah’s Ark’ for them in the tumultuous waters of the Arctic Ocean. At the same time, it serves as a unique model territory for studying the life of polar bears ashore. This territory makes it possible to observe how polar bears respond to these conditions of melting sea ice; whether they are able to survive on land, and for how long, without being able to hunt their main prey. This makes it possible to assess their adaptability and their response to the various dangers lying in store for them on the mainland.

All forecasts imply that sea ice will continue to melt. It is unknown how long this process, caused by global warming, will last, as well as the scope of its potentially disastrous consequences. At any rate, the regional climate and, consequently, ice floes and sheets will continue to change in the next few years and, even more likely, decades, impairing the habitat of polar bears.

How unique and dangerous are such developments for the polar bear population? The polar bear is the youngest species in the bear family. The modern polar bear evolved during the Middle Pleistocene period, circa 200,000-120,000 years ago. This is confirmed by palaeontological data and DNA analysis/profiling of modern and ancient polar bear forms. There is credible evidence, corroborated by modern science, suggesting that the Middle and Late Pleistocene periods were characterised by ancient ice ages and ocean transgressions, namely the rising level of the world’s oceans. Also, research suggests that cyclic ice ages occurred during the Pleistocene and Holocene periods. A comparison of the polar bear’s evolutionary history with palaeoclimatological data shows that the polar bear survived at least four global warming periods during its existence on this planet, and that these periods exceeded the current global warming period by thousands of years. Palaeontology shows that Pleistocene polar bears were considerably larger than modern polar bears, that they roamed Arctic territories, North Atlantic islands, and the Baltic Sea basin, including the Baltic coast. Also, they lived in coastal ecosystems overlapping with forest fauna or bordering on it.

How did this unique Arctic predator, endemic to drifting sea ice, manage to survive the disappearance of the ice, and for so long? What conclusions should we draw from this historical excursion today?

A study of modern polar bears’ behavioural ecology during their periods ashore makes it possible to answer some of these questions. This is important in order to assess the state of the polar bear population and its changes; to comprehend the adaptive stability of animals, that is, their ability to quickly adapt to rapidly changing conditions; to identify factors threatening the existence of the species; and, finally, to chart essential protective measures.

Why are polar bears so attracted to Wrangel Island? The island offers much of what a polar bear needs to survive. Wrangel Island is a large landmass with extremely diverse terrain located in the centre of a high-yield Arctic Ocean sector. The island’s high density of the main animals that polar bears hunt creates favourable hunting opportunities in this area of the ocean. Female polar bears can find good dens in the island’s mountain areas. Against the backdrop of dwindling ice, the island becomes a refugium for polar bears, enabling them to live through open-sea periods. Since the island is a natural reserve, polar bears are safe there.

So, what do we see on Wrangel Island? What conclusions can be drawn from observations there?

Ice conditions in the vicinity of the island began to change drastically in 1990. Melting ice floes deprive polar bears of an optimal habitat. Consequently, polar bears have to spend several months ashore each year. They come ashore during the last stages of an ice floe’s disintegration. The animals reach land in the coastal areas nearest to their respective ice floes, on which they have hunted during that period. Most polar bears in the north-eastern Russian Arctic come ashore on Wrangel Island. The rest wade onto the Chukotka coast and north-western Alaska. Some bears remain on the edge of pack ice drifting towards circumpolar areas. Consequently, the polar bear population is divided into four seasonally isolated populations each year. The proportion of animals going ashore in various areas depends on the ice movement during the ice disintegration process.

The increased number of polar bears in coastal areas does not mean their population is growing. Rather the opposite, they are facing a critical situation – they have lost their primary areas of habitat and the opportunity to hunt seals in the sea ice. This is a difficult period for the polar bear population. As soon as the sea freezes in winter, the bears promptly leave land and start hunting in the ice – they only stay on the mainland as long as there is no ice. When threatened, during the absence of ice, they literally swim off into the open sea. They are forced to swim long distances before they can find suitable ice floes. This saps their strength and considerably reduces the chances for survival.

The overland polar bear population varies depending on ice conditions and the total number of polar bears. In the early 1990s, hundreds of polar bears found refuge on Wrangel Island. In September 1990, up to 160 polar bears were sighted near just one walrus rookery at Cape Blossom. In the past few years, the polar bear population on the entire island has not exceeded 200-300 bears. In the past few years, the ‘coastal’ polar bear population has not exceeded 500-700, including bears roaming the Chukotka and Alaska coasts. Fewer pregnant female polar bears hibernate inside dens on the island. In the early 1990s, the number of local dens was estimated at 350-400. In recent years, the most optimistic estimates put that number at no more than 60-70.

It is unclear how many bears drift away on pack ice towards circumpolar areas in summer. Their subsequent destinations are also unknown. US scientists have tagged polar bears with satellite collars off the Alaska coast to track their movements. In recent years, virtually all of the bears either reached Wrangel Island in late summer and autumn, or drifted on ice formations to the north of the island. In effect, polar bears migrate from the United States to Russia. Some of the bears tagged near the Canadian Arctic Archipelago in the Beaufort Sea also reach Wrangel Island.

The bears have also faced somewhat difficult seasons ashore during land-based research. They were unable to find food and became malnourished. Dead bears were discovered when the percentage of malnourished bears reached 7-15% of the entire population. But there were also some favourable periods when the bears could find enough food ashore. Observations have revealed that even after the disintegration of ice floes that polar bears can find their principal prey species in coastal ecosystems.

The walrus and Arctic seal populations are also closely linked with drifting ice floes. When the ice melts, walruses form coastal rookeries, and seals also come ashore to rest, which means the polar bears can then hunt them here. They pick on the carcasses of dead marine mammals, including grey whales washed ashore. The number of carcasses may be quite impressive because walrus and seal mortality rates tend to go up in such years. Due to heightened storm activity in an ice-free Arctic Ocean, additional organic matter is washed ashore. In such conditions, polar bears eat anything they can find. They pick up fish, eat any carrion on the coast and in the tundra. Researchers have seen polar bears try to hunt musk oxen on the island. One such attempt proved successful. They also hunted salmon in a local river, as well as lemmings during the peak lemming season.

Wrangel Island studies have revealed that, despite their evolved specialisation as ice-borne hunters that catch marine mammals, polar bears have retained qualities that secure their environmental flexibility. These qualities include high intellect, an ability to learn fast, an ability to eat a wide range of food and to easily adapt from solitary life amidst masses of ice to community life with other polar bears. The social life of polar bears is particularly interesting. It turns out that this solitary wanderer, which roams the vast expanses of the Arctic, displays the traits of a highly socialised animal. Unlike wolves, polar bears are not collective hunters. But they are collective eaters. When gathering in large groups near food sources, including walrus rookeries or whale carcasses, polar bears display remarkably high social tolerance without the slightest sign of aggression, dealing with each other in a wide range of communicative behavioural forms. These important qualities facilitate the survival of the polar bear population under changing conditions. Humans can learn a lot from these bears’ adaptability.

Polar bears have not lost the skills inherited from their brown bear ancestors during the ‘settling’ of the Arctic sea ice cover. On the contrary, they have improved these skills and acquired new ones. In response to the question of whether the polar bear has a future in the face of global warming, we can answer in the affirmative. Due to the above qualities, the polar bear can survive lengthy warming periods and ice disintegration by relocating to coastal ecosystems. But new dangers await them in the modern world.

The current global climate change is quite unique because polar bears have never before faced warming periods in conditions of such high human population density and activity in the Arctic. Polar bears will survive the current warming period just like they had survived all others unless they are exterminated by humans.

It should be recalled that this species found itself on the verge of extinction in the first half of the 20th century – in the 1950s and 1960s – when massive hunting was taking place for polar bears in the Arctic. Using firearms and all-terrain vehicles, hunters killed hundreds of polar bears. In just 25 years, polar bears became a vanishing species. And this happened at a time when they enjoyed favourable ice conditions. Only active protection, a complete ban on sport and commercial hunting, and international efforts to protect the polar bear population helped save the species. Russia played the most prominent role in this respect, as it completely banned any polar bear hunting as of January 1, 1957.

Climate change now has a negative impact on the polar bear population. Negative factors include:

1. Optimal ice-floe habitats turn into marginal habitats during the summer/autumn season and can be completely excluded from the bears’ life cycle.

2. An increasing number of bears are exposed to the extreme high-seas environment. They find themselves in the open sea and are forced to swim for long periods. This causes exhaustion, injuries,and a higher mortality rate.

3. An increasing number of bears are forced to go ashore and to live there for longer periods without being able to hunt their main prey. The bears can become malnourished, and for longer periods.

4. The reproductive cycle of polar bears is disrupted.

5. Due to dwindling sea ice and forced landfall, the chances for encounters between polar bears and humans increase considerably, which is fraught with violence and the shooting of animals.

While on the mainland, polar bears either sleep or wander slowly in search of food along the coast. Given the current human population density along the Arctic coast, the bears inevitably approach human settlements, where encounters are likely. This places a special responsibility on us for the future of polar bears and the promotion of a safe coexistence in the Arctic.

Most polar bears are killed by humans, rather than by global warming. The main threats to their survival in the modern world are manmade. First, this includes poaching, the never-ending aboriginal hunt for polar bears on the North American continent, the shooting of polar bears wandering into communities, and other human-provoked shooting incidents, the pollution of the Arctic, the industrial impact on polar bear habitats, and the nuisance factor when polar bears are studied with the help of so-called invasive methods, including pursuit by helicopter teams for subsequent catching and immobilisation. In such cases, researchers can inflict pain on polar bears or become a stress-provoking factor.

The ground-based study of the polar bear population by non-invasive methods, which do not interfere with the natural pace of their life, makes it possible to answer questions as regards the species’ response to current changes in their living conditions. Research involving the use of satellite telemetry technology and other technological methods of analysis make it possible to specify and augment these findings:

1.A reduction in polar bear populations. Quite possibly, some populations may disappear due to shifting habitats and increased mortality rates when warming becomes more destructive.

2. The redistribution of the species’ habitat across the entire Arctic.

3. Increased genetic exchange between populations.

4. The seasonal division of some populations into isolated subpopulations, or so-called population fragmentation.

7. More bears hibernate on drifting ice floes. This implies high-risk life at hibernation sites and greater chances of losing their offspring.

8. Increased polar bear socialisation during periods ashore.

However, all this will not make the polar bear disappear as a species. The real threat to the existence of polar bears is that humans can easily kill them when these animals live on land.

What can we do to help polar bears survive in the modern world? How can we save them? Our current knowledge allows us to determine what must be done to save the polar bear population:

New specially protected nature areas must be established in the Arctic, especially in locations that serve as refugia for polar bears.

Effective protection must be established for maternity den sites. Female polar bears must not be disturbed during the most vulnerable period of their lives.

Effective anti-poaching measures are required, and the human-provoked shooting of animals must be prevented.

Lethal conflicts during encounters between humans and polar bears must be eliminated with the help of non-lethal weapons. A system must be enacted for safe human conduct in the Arctic, providing for the protection of both humans and polar bears.

Polar bears must not be disturbed in their natural habitats.

Experts must monitor the state of populations and population change trends.

Experts must monitor the state of habitats.

We must act in order to stop the current global warming period from ending the history of polar bears on Earth.

Nikita Ovsyanikov is Deputy Director for Research, Wrangel Island Nature Reserve; PhD in Biology; Member of the Polar Bears Specialist Group of the International Union for the Conservation of Nature (IUCN) Species Survival Commission, and member of a working research group at the US-Russia Polar Bear Commission